1. Field of the Invention
This invention relates to a method and device for displaying simulated 3D space as an image.
2. Description of the Prior Art
Ordinary 3D displays have adopted the presentation of parallax. 3D image display devices employ either a viewer-worn display or a stationary display. The most common viewer-worn display is the head-mounted display (HMD). While this display can impart a 3D perception including distance and does not restrict the activity domain of the image viewer, it puts a severe physical burden on the viewer such as by producing feelings of heaviness confinement and causing eye fatigue. The display is therefore difficult to use for long periods. Production of high-resolution images with a viewer-worn display is, moreover, difficult using currently available technology.
A stationary display puts less burden on the viewer than one worn by the viewer. However, devices using this type of display have been incapable of synthesizing images that the viewer perceives as three-dimensional when the display is distant from the viewer""s eyes (beyond the fusion limit). This is because human 3D perception depends both on binocular parallax at short distances and on focus information (in the approximate range of 0-3 meters from the eyes).
Although this problem can be overcome by putting the stationary display near the viewer, this method restricts the viewer""s range of movement and makes viewer interaction with the 3D image impossible. When using a stationary 3D display for teleoperation or as a simulator for training, therefore, the only option available has been to project the 3D image to a place apart from the viewer. This has made it impossible to convey a strong perception of realism to the viewer. As a concrete example, FIGS. 6(a) and 6(b) show a viewer 23 attempting to teleoperate jobs performed by a robot 21 in a workspace 22 in front of the robot 21. In order to secure a certain amount of open space (elbowroom) 26 for the viewer 23, the display 24 has to be positioned at a location apart from the viewer 23. Moreover, owing to the fusion limit, the projected workspace 25 displayed on the display 24 must be formed at a position apart from the viewer 23. The viewer 23 therefore does not experience sufficient realism and has difficulty in carrying out operations accurately.
The fusion limit will be briefly explained. In a 3D display method using parallax, a discrepancy arises between the depth estimated from the thickness of the eye lenses responsible for adjusting focus and the depth calculated from parallax. When, as shown in FIG. 7, parallax images 35a and 35b are presented to a viewer 32 situated apart from the display 31, the depth of the images estimated from parallax is perceived to be at the line-of-sight intersection point 37. Moreover, since the image for the right eye 35a passes through the lens 33a of the right eye and is focused on the retina 34a of the right eye and the image for the left eye 35b passes through the lens 33b of the left eye and is focused on the retina 34b of the left eye, the depth of the images estimated from the thickness of the eye lenses is perceived to be at a position 36 midway between the images 35a and 35b. This gives the viewer a feeling of unnaturalness. As human depth perception uses focus information in preference to parallax information when viewing nearby objects, this feeling becomes particularly strong if the viewer is forced to make stereoscopic observations at short range. Moreover, when a real object 38 such as the viewer""s hand comes into the field of vision as shown in FIG. 8, the viewer experiences a very strong impression of mismatch that arises because the parallax of the presented image and the parallax of the hand arise at approximately the same location but the viewer cannot focus on two points at the same time.
To overcome the foregoing problems, it is necessary to provide a 3D display fulfilling the following three requirements.
i) To reduce the physical burden on the viewer by using a stationary display to present images.
ii) To enable short-range 3D perception without giving the viewer a feeling of unnaturalness.
iii) To provide open space sufficient for the viewer to interact with the 3D image.
An object of this invention is to meet these requirements by providing a method and device for displaying simulated 3D space as an image that does not place a physical burden on the viewer even during long-term use, that does not give the viewer a feeling of unnaturalness even regarding short-range 3D perception, and that offers enough open space for the viewer to interact with the 3D image.
For achieving these objects the invention provides a device for displaying simulated 3D space as an image comprising:
an image display apparatus having an image display section for presenting a different image to each eye of a viewer, and
a convex lens for presenting as a real image within reach of the viewer""s hands a 3D image produced from the images displayed at the image display section by parallax between the eyes.
The invention further provides a method for displaying simulated 3D space as an image comprising:
presenting a different image to each eye of a viewer by use of a 3D image display apparatus having an image display section, and
using a convex lens to present as a real image within reach of the viewer""s hands a 3D image produced from the images displayed at the image display section by parallax between the eyes.
Thus, by positioning a convex lens in front of the image displaying surface of an image display apparatus capable of presenting each eye with a different image, the invention presents a 3D image as a real image within reach of the viewer""s hands. As the image is therefore formed at a position substantially matching the position estimated from parallax between the left and right eyes on condition that the image is presented within the operation space (within reach of the viewer""s hands), it conveys strong realism with no feeling of unnaturalness.
The above and other features of the present invention will become apparent from the following description made with reference to the drawings.